This invention relates to an instrument for removing unwanted obstructions in the milk duct of a cow teat which hinder or stop the flow of milk therethrough. More particularly, this invention is directed toward a simplified unitary knife structure for safely and thoroughly removing scar tissues, small floating cysts, tumors and the like from the interior of the milk duct of a cow's teat.
In the dairy industry, it is not uncommon to encounter difficulty in obtaining milk from one or more teats of a particular cow. This is usually caused by an obstruction of scar tissue, membrane cartilage or other growth within the milk duct of the teat and severely curtails the milk production from the cow. Various devices have been proposed over the years for clearing the duct of the teat from these obstructions, with most of them being of the curette type for actually severing a growth from the lining of the milk duct to various multiple acting instruments for removing growths which have required manipulation of at least two elements requiring generally the use of two hands to affect the desired clearing of the milk duct. U.S. Pat. Nos. 1,837,503; 1,663,761; and 737,293 are typical of this type of apparatus where a hollow shaft has an aperture forming a cutting surface in the distal end and a rod positioned in the shaft interior has a cooperating surface for severing a protrusion captured by said aperture. The manipulation of the interior and the exterior actuating members usually requires two hands. Another approach has been that of U.S. Pat. No. 2,816,552 in which a set of knives is expanded by an internal threaded rod which expands flexible blades to an enlarged diameter so that the interior of the milk duct can be scrapped to enlarge same and remove undesired obstruction. Various veterinary knives have been proposed which can be manipulated to remove tissue from the interior of the milk duct of the teat and these are represented by U.S. Pat. No. 2,676,595.
All of these prior art devices have been difficult to use or have required the expert services of a veterinarian to properly remove the obstruction without injuring the teat of the cow. While some of these devices have permitted removal of the obstruction, they have frequently caused additional injury to the teat and ultimately resulted in lack of milk flow, resulting in premature termination of the milking life of the cow.